Reseeding

Published 5 June 15

Too often, reseeding decisions can be poorly judged and made in a hurry. Resulting in poor seed bed conditions, patchy establishment and a new ley which is not fit for purpose, says independent grassland and soil consultant Chris Duller. Just as any other on-farm investment, reseeding should be well planned and based on sound information.

Target the right fields for reseeding.

Identify which fields are underperforming, ideally based on numbers rather than guesswork. Grass growth rates, yield data and stocking rates tell you which fields are struggling. Look closely at the percentage of ryegrass and weeds. Identification is easier at this time of year with a lot of weed grasses, like rough stalk meadow grass, in head. Any pasture containing less than 40% ryegrass should be on your list of possible candidates for reseeding.

Image 1 Silage fields can soon fill up with rough stalked meadow grass (top), with a D-value 20% less than ryegrass (bottom)

However, it might not be the worst fields that offer the best return on investment when it comes to reseeding. Wet pieces, dry banks and north-facing fields are not the place to spend your money at the minute. Instead, concentrate on the nice square, flat fields with good soil depth and drainage, which should be growing more grass. All your best fields should have 70%, or more, ryegrass, and grow well over 12t DM/ha.

Sort out problems before you start

Why does the field need reseeding? If you don’t find out why it has gone backwards and correct any problems, it is likely that a new reseed will quickly end up as the old one. A soil test and digging a few holes, to check for soil compaction, are two vital tasks in a reseeding plan.

Ground lime is likely to take a couple of months before it has a big impact on raising soil pH. If a pasture needs liming, consider applying half now and then again in the seed bed.

It might be possible for compaction damage to be ploughed out, or it may need subsoiling/lifting. Surface seeding or minimal tillage won’t be effective if you have soil compaction issues.

Weed and pest control

Don’t miss out on the chance reseeding gives to control problem weeds such as docks, nettles and thistles. Give glyphosate a decent target, don’t skimp on application rate and make sure you get a good kill before cultivating (probably around five days at this time of year).

Bearing in mind a reseed will cost around £500/ha, it makes sense to consider a small investment, of about £7/acre, to control leather jackets and frit fly when going from grass to grass.

Seed bed conditions

The key aims of any cultivation are to destroy the old sward, break up any soil compaction, bury weed seeds, incorporate any muck/slurry, and then provide a good environment in which a seed can germinate and grow. It sounds easy, but every soil and season is different.

Beware the main problems:

- Overworked seedbeds – normally due to the dreaded power harrow. You will need some fine material at the surface for good soil/seed contact, but you also need to maintain some blocky structures in the soil to prevent everything from slumping and compacting. An overworked seedbed is more likely to cap off, giving risks of soil erosion and seeds can easily be drilled too deep.

- A ‘good covering’ of muck or slurry is recommended but don’t go mad, 2–3,000 gallons/acre of slurry, or four or five tonnes of FYM/acre is a good target to avoid problems with seed bed consolidation and poor germination conditions. Top up with bagged phosphate if you have low P indexes: phosphate is crucial for rapid establishment.

- Spongy seedbeds – if you think you need to roll again, you do. Tight seed beds will keep moisture in and prevent seed from going too deep, and will help prevent damage in early grazings.

Seed mixture selection

Think carefully about what you want the ley to do and let your seed merchant know exactly what it is you want. Over 70% of seeds sold in UK are ‘cut and graze’ off the shelf mixtures. Would you be better off with a specialist grazing mixture to give you better ground cover, and better early season growth and quality, or should you take advantage of a specialist silage ley with hybrids and Italians that could give you an extra 5t DM/ha?

The type of mixture is the most important decision you’ll make, the variety choice is fine-tuning. Use the Recommended Grass and Clover Lists and question your merchant about every variety in his mix, ask why is it there, what are its good qualities?

Keep heading dates as close as you can (seven-day spread) to make management easier and maintain quality. Don’t skimp on seed rate.

After-care

If you need to control germinating weeds, do it early when they are small. This means walking your reseed twice a week for the first four or five weeks of its life. Sprays are far more effective when the world is warm. Something that is worth remembering when you are reseeding in September and spraying in October.

Graze when ground conditions are good to encourage tillering. Ideally, you want to be in and out in a day or two, taking it down from about four or five inches to two inches. It’s important to give the reseed an easy winter, so don’t plaster it with slurry, and feed it early next spring.

Reseeding can be an excellent investment if it’s done right. New leys can recoup the £500/ha reseeding costs in their first season, with an extra 4 or 5t DM/ha yield, and then sustain high yields and quality for many years to come. This sort of success will only come if the whole reseeding operation is well planned and well executed.